To ensure the safety of a vehicle during travel requires provision of a sensor that detects angular velocity and acceleration. When such a sensor is installed in an environment like an engine room where the range of temperature variations is extensive and vibrations and electromagnetic noises are significantly influential, it is necessary to devise measures to keep the sensor outputs highly reliable.
The sensors used in such circumstances are thus internally equipped with self-diagnostic functions that output diagnostic information along with the sensor outputs to an external device. On the basis of the received diagnostic information the external device determines if received sensor output is normal and whether to adopt the sensor output.
Patent Literature 1 and 2 describe sensors which detect physical quantities such as angular velocity and acceleration and which transmit the results of such detection and intra-sensor fault diagnosis to the external device.
In the technique described in Patent Literature 1, a fault diagnosis signal given at the same point in time as a sensor signal is output by an output circuit on a time-division basis. The external device determines whether the sensor signal to be output at the next point in time is normal according to the fault diagnosis signal.
According to the technique described in Patent Literature 2, if the sensor part is determined to be at fault, the sensor signal is output from a first output terminal as a signal outside the normal output voltage range, and the fault diagnosis signal is output from a second output terminal to the external device.